<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        /*.box{*/
        /*height: 700px;*/
        /*width: 800px;*/
        /*border:1px solid #2e6da4;*/
        /*}*/
        #auto{
            position: absolute;
            top:50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 300px;
            height: 300px;
            background: #2e6da4;
        }
    </style>
</head>
<body>
<div id="auto">测试</div>
</body>
</html>